Lets talk weight

[ryude]

Originally Posted by fatoni

that only makes sense if you make a car and then turn it into a convertible. mazda is and has always been very concerned about weight and i dont think toyota will be able to close in on that the first run through.

aside from that i bet toyota sticks some huge wheels on the thing too. its not going to be under 2600lbs and the current miata weighs more than the 24xx mentioned earlier

A convertible is a convertible, you have to beef up the frame in order to keep the body from twisting when making hard turns. A connected roof already keeps the body rigid, a convertible has to have extra material added to the frame because it has no connected roof. And where do you think this added weight goes? At the very top of the car, the worst place for weight to be.

[WolfpackS2k]

Originally Posted by ryude

A convertible is a convertible, you have to beef up the frame in order to keep the body from twisting when making hard turns. A connected roof already keeps the body rigid, a convertible has to have extra material added to the frame because it has no connected roof. And where do you think this added weight goes? At the very top of the car, the worst place for weight to be.

THANK YOU! That's exactly what I was going to say. It's common sense people. I know not everyone took structural engineering classes but you don't have to be an engineer to realize a vehicle with a fixed roof will inherently be stiffer, requiring less additional support and thus belighter than a convertible. Without a doubt the S2000 would be lighter if it was a fixed roof coupe from inception.

[Random_Art]

Originally Posted by Allch Chcar

When did you become such a smartass? I kid I kid.

The Celica has nothing in common with the FR-S/BRZ.

I just know that the 2012 Impreza is 2950lbs and the Coupe is going to be lighter. Dunno what else to say .

We can guess that it'll be somewhere between the 7th gen Celica and the 2012 Impreza.



But, you're right. They don't have anything in common except for size, and the assumption that if they seriously want to keep the weight down, they would use similar, if not better, building materials and chassis engineering techniques. We can count on a bit of added weight for the RWD components and differing suspension (I think someone in a different thread was saying that double wishbones are heavier than macpherson struts.) So add another 150-200lbs for that stuff. Of course these are just estimates, I have no idea how the weight would actually differ with that stuff.
The FR-S also has a trunk rather than a hatch like the Celica. A bit of weight can be cut from not having to over compensate for the added flex that you get from a liftback design.

I'm just trying to use the Celica as an example of what Toyota can do when they get serious about weight. I'm hoping for 2500lbs as the curb weight. I expect it to be somewhere around 2650.

[Allch Chcar]

Originally Posted by Random_Art

We can guess that it'll be somewhere between the 7th gen Celica and the 2012 Impreza.

[IMG][/IMG]

But, you're right. They don't have anything in common except for size, and the assumption that if they seriously want to keep the weight down, they would use similar, if not better, building materials and chassis engineering techniques. We can count on a bit of added weight for the RWD components and differing suspension (I think someone in a different thread was saying that double wishbones are heavier than macpherson struts.) So add another 150-200lbs for that stuff. Of course these are just estimates, I have no idea how the weight would actually differ with that stuff.
The FR-S also has a trunk rather than a hatch like the Celica. A bit of weight can be cut from not having to over compensate for the added flex that you get from a liftback design.

I'm just trying to use the Celica as an example of what Toyota can do when they get serious about weight. I'm hoping for 2500lbs as the curb weight. I expect it to be somewhere around 2650.

There is a rumor, now I don't want to concern anyone, but there was a rumor about the prototype weight posted by a guy on NASIOC. I tried to ask about where he got that info but someone else piped in with the height since it was in bold(didn't notice). And so he never answered my question.

[blur]

hmm. 2500lbs is the magic number. Also, I'm excited that they stated this car will have the lowest center of gravity in a production car, period. I'm guessing with that kind of dedication we may just get a number that is fitting of the car's goals.

[fatoni]

Originally Posted by ryude

A convertible is a convertible, you have to beef up the frame in order to keep the body from twisting when making hard turns. A connected roof already keeps the body rigid, a convertible has to have extra material added to the frame because it has no connected roof. And where do you think this added weight goes? At the very top of the car, the worst place for weight to be.

i understand that but you have to consider that a roof of a car is also at the very top of the car, the worst place for the weight to be. you call it added weight but but kind of omit the fact that roofs weigh something. on top of that roofs have to be roof shaped. added strutctures dont have to cover passengers so the can be shaped to put rigidity and weight first instead of an afterthought. how do you explain the elise? its plenty rigid and yet it doesnt have a structural roof. all that and it comes in at under 2000lbs. do you think that a fixed roof elise would drop 200 lbs?

[fatoni]

Originally Posted by blur

hmm. 2500lbs is the magic number. Also, I'm excited that they stated this car will have the lowest center of gravity in a production car, period. I'm guessing with that kind of dedication we may just get a number that is fitting of the car's goals.

it isnt going to have the lowest cg period. just in its class. and lets hope the get it all right because cg isnt everything, at least that is what things like the 911 should be teaching us.

[Dave-ROR]

Originally Posted by fatoni

i understand that but you have to consider that a roof of a car is also at the very top of the car, the worst place for the weight to be. you call it added weight but but kind of omit the fact that roofs weigh something. on top of that roofs have to be roof shaped. added strutctures dont have to cover passengers so the can be shaped to put rigidity and weight first instead of an afterthought. how do you explain the elise? its plenty rigid and yet it doesnt have a structural roof. all that and it comes in at under 2000lbs. do you think that a fixed roof elise would drop 200 lbs?

The Elise has (or had, not sure these days) a special permit to get around many of the safety standards required of normal cars, it also has an integrated roll bar. A fixed roof elise wouldn't drop weight, but it's NOT a convertible either.

Most convertibles have power motors, very heavy steel frames for the softtop that requires springs, locking mechanisms and a lot of steel bars, etc.

By comparison, sheet metal and stamped bracing is pretty light and hugely increases torsional rigiidity.

Convertibles can be stiff (S2000 for example, modern miatas are good too, old miatas were floppy as hell) when it's made to be a convertible but there is a LOT of extra weight added in that top and the additional bracing, bigger a pillar braces, factory roll bars in some cases, etc.

[Dave-ROR]

Everything will come down to how the car drives for me. If the car is a blast to drive and, most importantly, involves the driver and communicates with the driver through every possible interface, then I don't give a rat's behind how much it weighs, how fast it is, etc. It'd be a driver's car, and that's exactly what I want.

If Toyota/Subaru refines it to the point that it stops being communicative with the driver, etc, then the car is dead to me even if it weighed 2000lbs with 500hp.

[blur]

Originally Posted by fatoni

it isnt going to have the lowest cg period. just in its class.

Source?

[Aki]

Originally Posted by fatoni

i understand that but you have to consider that a roof of a car is also at the very top of the car, the worst place for the weight to be.

Doesn't matter, even if the weight is the same the benefits of added rigidity from a fixed roof far outweigh the negatives. Take the Z4 coupe/convertible from 2008:

Z4 convertible: 3086 lbs
Z4 coupe: 3108 lbs

That's only a 22 lbs difference. But then you look at the difference in torsional rigidity--24,000 lb/ft per degree of body twist on the coupe compared to 10,700 lb/ft per degree on the roadster, and you see the coupe is far superior for performance.

Also, the premise on why Mazda opted for a convertible is a bit off. They didn't choose a roadster because that was the best for performance, they chose a roadster format because they wanted a small RWD car reminiscent of the old British roadsters, like the Triumph TR6 or MGB. Honda went with a droptop for the S2000 for a similar reason--because it riffed off the Honda S600.

[fatoni]

Originally Posted by Dave-ROR

The Elise has (or had, not sure these days) a special permit to get around many of the safety standards required of normal cars, it also has an integrated roll bar. A fixed roof elise wouldn't drop weight, but it's NOT a convertible either.

Most convertibles have power motors, very heavy steel frames for the softtop that requires springs, locking mechanisms and a lot of steel bars, etc.

By comparison, sheet metal and stamped bracing is pretty light and hugely increases torsional rigiidity.

Convertibles can be stiff (S2000 for example, modern miatas are good too, old miatas were floppy as hell) when it's made to be a convertible but there is a LOT of extra weight added in that top and the additional bracing, bigger a pillar braces, factory roll bars in some cases, etc.

i agree that most convertibles are heavier than coupes but my point is that most isnt good enough to say that if x convertible weighs y, z coupe should be lighter than x.

[fatoni]

Originally Posted by blur

Source?

dont remember but whats yours? i might be wrong but i seriously doubt a 20k car, likely with a steel roof is going to have a lower cg than things like the lfa or ariel atom

[fatoni]

Originally Posted by Aki

Doesn't matter, even if the weight is the same the benefits of added rigidity from a fixed roof far outweigh the negatives. Take the Z4 coupe/convertible from 2008:

Z4 convertible: 3086 lbs
Z4 coupe: 3108 lbs

That's only a 22 lbs difference. But then you look at the difference in torsional rigidity--24,000 lb/ft per degree of body twist on the coupe compared to 10,700 lb/ft per degree on the roadster, and you see the coupe is far superior for performance.

Also, the premise on why Mazda opted for a convertible is a bit off. They didn't choose a roadster because that was the best for performance, they chose a roadster format because they wanted a small RWD car reminiscent of the old British roadsters, like the Triumph TR6 or MGB. Honda went with a droptop for the S2000 for a similar reason--because it riffed off the Honda S600.

that is a great argument as to why a convertible is inferior to a coupe but that isnt what this thread was about. it was about weight and i think you just proved my point.